This invention relates generally to computer networks. In particular it pertains to a relatively low cost network switching hub and bus structure integrated into an integrated circuit chip, which improves network performance by increasing bandwidth and reducing collisions.
Personal computers (PCs) have permeated nearly all levels of society and business, creating a need to link individual PCs into networks to more efficiently utilize and share resources. Computer networks are becoming increasingly popular in low-cost, performance-oriented computing environments.
One very popular type of network used to link PCs or workstations is called a local area network (LAN). LANs and other types of networks permit the sharing of resources such as software, printers, modems, and other peripherals among PC workstations operating as nodes on the network.
FIG. 1 illustrates a simple and conventional LAN, generally designated by the reference numeral 100. Network 100 comprises a plurality of PC workstations 112a through 112e, each connected by a communication link 113a through 113e respectively to an associated hub 114. Communication links in such networks are typically two-conductor cables, wherein a potential across the two conductors is varied in a manner representing sequential binary data. Such a link is termed a serial link.
Hubs, such as hub 114, in networks are used to connect multiple workstations for routing through a single link to a server. In FIG. 1, PC workstations 112a through 112e are all connected to server 116 through link 115. Hubs typically have a limited number of input ports so the number of workstations that can be connected is limited as well. Typically the input ports are arranged in groups of 8, 16, 32, 64 and so forth. Further network capacity can be added by connecting multiple hubs, such as hub 118 (shown in dashed lines) to the one file server, and the additional hubs may then be connected to other multiple workstations (not shown). Other network variations include addition of multiple file servers connected in different arrangements to multiple hubs.
File server 116 in this example, and generally in the art, comprises a set of sheared high-capacity mass storage devices, such as hard disks. Such file servers are often special PCs that have higher performance capability and more and larger capacity hard disks than do individual workstations 112a through 112e. The shared disk space on such file servers typically stores software applications which spreads the cost of the hard disk over more than one user, thereby permitting more efficient use of resources.
File server 116 in this example may also contain routers (not shown) for communication and connection to different network protocols such as Ethernet(trademark), Asynchronous Transfer Mode (ATM), and Fiber Distributed Data Interface (FDDI), among others. The output of file server 116 is coupled to shared peripherals such as a network modem 118, a laser printer 120, and other peripherals represented by element number 122. All workstations 112a through 112e on the network share access to the peripherals connected to server 116.
It will apparent to those with skill in the art that the example of FIG. 1 is but one of many network arrangements known in the art.
There are some limitations of a conventional LAIN 100 as described above. For example, communication over link 115 is shared by all of the workstations, and if many workstations are attempting to communicate at once, bandwidth may be a problem slowing communication. By way of example, coaxial lines used in many networks have a maximum data transfer rate of 10 megabytes per second (Mb/s). The maximum data transfer rate, which is related to bandwidth, ultimately determines the maximum number of workstations that can be adequately handled by the network. Overloading a network can result in lost connections communication delays, slow system response timeouts and slow file transfer times. All of these situations decreases the efficiency of the network and become very annoying to network users.
Another limitation of conventional LANs such as LAN 100, is that communication collisions may occur between multiple workstations requesting access to the network. In commonly used network protocols such as Etheme(trademark), one way that collisions are handled is by processing one request at-a-time while buffering other requests in a first-in-first-out (FIFO) buffer. Since access is granted one-workstation-at-a time, other stations are required to wait, thereby decreasing efficiency. Networks with heavy traffic tend to have many collisions which may drop efficiency to unacceptable levels.
The problems of inefficient communication are exacerbated by addition of more workstations to the network and increased use of bandwidth-hungry applications such as color publishing and document imaging. So networks that had adequate bandwidth when installed may be outdated simply by software development.
Another way to add bandwidth is by increasing the number of switching hubs. This solution often results in segmenting a single large network into multiple smaller networks which decreases the amount of traffic that travels over any given communication link and thereby increases the bandwidth available to each individual user. Statistics and traffic patterns can be further analyzed for adjustments for optimal network performance.
Another disadvantage of conventional networks is the relatively high cost of multi-port hubs. By way of example, a 32 or even 16 port hub for some networks can cost in the range of about 32K to 100K dollars, a substantial investment for any user. Also conventional hubs are typically separate units in an enclosure with a dedicated power supply and controlling electronics, adding to clutter and adding to cost.
What is needed is a switchable hub that is relatively low cost, compact, and increases network performance by increasing bandwidth and reducing collisions. As will be described hereinafter, the present invention provides a method and apparatus to meet these objectives.
In a preferred embodiment an integrated circuit (IC) switching hub is provided, comprising a parallel bus of n bus lines implemented as traces on the IC; a first data port adapter controller connected by n first port lines through a first output buffer to the bus, each first port line connected to a bus line source-to-drain through one of a set of first queue switch transistors, and connected to a first data port providing a first external data link for the switching hub; a first read amplifier connected by n first receiver lines one each directly to each one of the n bus lines, and by a first data link to the first port adapter controller; a second data port adapter controller connected by n second port lines through a second output buffer to the bus, each second port line connected to a bus line source-to-drain through one of a set of second queue switch transistors, and connected to a second data port providing a second external data link for the switching hub; a second read amplifier connected by n second receiver lines one each directly to each one of the n bus lines and by a second data link to the second port adapter controller; and an arbitrator controller connected by a first control line to the gates of the first set of queue switch transistors, by a second control line to the gates of the second set of queue switch transistors, by a third control line to the first port adapter controller, and by a fourth control line to the second port adapter controller. The arbitrator controller is adapted to switch data from the first and second port adapter controllers onto the bus through the first and second output buffers and the first and second sets of queue switch transistors by switching the gates of the transistors via the first and second control lines respectively, and adapted to transfer data from the bus to the first and second external data links via the first and second read amplifiers through the first and second port adapter controllers by enabling the respective port adapter controllers via the third and fourth control lines respectively according to a preprogrammed arbitration scheme.
In some embodiments the first and second port adapter controllers share a single read amplifier the read amplifier being connected to both port adapter controllers via a single data link. There may be many more ports and port adapters as well either sharing receivers or not. Ports may be of any convenient nature, such a serial ports configured for network communication according to a standard protocol, such as Ethernet(trademark). Ports also may be of another sort, such as a PCI parallel port adapted for communication with a PCI bus, or an expansion port adapted for connection to a similar switching hub.
The IC switching hub in embodiments of the invention provides an ability to switch multiple packets without queuing and provides also greatly expanded band width for switching hubs, whereby, in some embodiments, cross traffic may be allowed without contention, depending on source and destination. The hub of the invention furthermore, is much more compact than prior art hubs, and by far less expensive than prior art hubs.